This section continues to provide expert physical and technological support for radiation treatment. This support consists of routine calibration and quality assurance of all radiation equipment and includes special dosimetry studies, computer-assisted treatment planning, and the design and development of special equipment tailored to special clinical needs. Regular checking of dosimetric and technical set-up aspects of radiation treatment will continue. 1. The improvement of the quality assurance (QA) program for the three Varian accelerators (Clinics 4, 18, and 20) and the Scanditronix Microtron M22 is an ongoing effort. A new quality assurance detector using five ionization chambers has been integrated into the QA program. This device consolidates output, energy and symmetry checks and will be useful for electrons as well as photons. 2. Adaptation of the radiation equipment and special supporting equipment for patient treatment and its implementation is a continuing effort, continually adjusted also to the needs of the ongoing and new clinical research programs. 3. The Microtron is to be replaced. 4. The computer programs for clinical radiation treatment planning are being rewritten in C-language for implementation on a Macintosh II system. This project is nearing completion and is being field-tested for both photon and electron beam treatment planning. An extensive "Help" manual has been assembled. 5. Supporting patient treatment and evaluation of clinical research.